Control unit assembly

ABSTRACT

A control unit for a medical device wherein the control unit comprises a pump, a conduit and control means for controlling the flow of fluid from the pump through the conduit; and wherein the conduit is a rigid internal passage located in the control unit.

BACKGROUND OF THE INVENTION

This invention relates to a control unit assembly for use with a medicaldevice and, particularly, a pneumatic medical device, such as acompression device for a limb. In particular, the invention relates to acontrol unit assembly for use with a mobile compression device suitedfor use in the treatment of venous leg ulcers, oedema, deep veinthrombosis and vascular disorders.

Various medical devices are known that require inflation of one or morecells with fluid to a desired pressure, for example, compression deviceswhich are used to apply pressure or pressure offloading devices such asmattresses or cushions which are used to even out pressure points.Compression devices are known for applying compressive pressure to apatient's limb. These types of devices are used to assist mainly in theprevention of deep vein thrombosis (DVT), vascular disorders and thereduction of oedema.

Prior art devices are adapted for use in a hospital setting in whichthey are used predominantly for the prevention of DVT in patients with ahigh risk for developing this condition. U.S. Pat. Nos. 5,117,812;5,022,387; 5,263,473; 6,231,532; 6,440,093 and 6,463,934 disclose suchdevices.

Compression therapy is used in the treatment of venous leg ulcers. Thetreatment relies on the compression achieving a reduction in oedema andimproved return of blood via the venous system. This in turn reduces theresidence time for blood supplied to the lower limb and the severity ofischaemic episodes within the limb that can result in tissue breakdown.

Compression of the limb can be achieved by a pnuematic or hydrauliccompression device.

WO 2004/084790 discloses one type of mobile compression device. By“mobile” it is meant that the user wearing the compression device hasrelative freedom to move about. The device of WO 2004/084790 comprisesone or more fluid inflatable cuffs containing one or more cells arrangedfor fitting on to a leg or an arm. The device allows the adjustment ofthe pressure in the cells dependent on the pressure profile desired. Theapplication of pressure by the cells in the sleeve or cuff is maintainedby a pump and valves which are operated by an automatic control unitwhich detects the fall or rise in pressure in each cell throughout thedevice. Where excessive or deficient pressure is detected by a sensorlocated in the cell, the control unit activates the pump to restore theintended pressure.

In the compression devices of the prior art, the control unit is aseparate component which is typically not integral to the compressiondevice and remotely operated. This is often on the user's belt, placedin a pocket or carried around by hand which is inconvenient for theuser.

As a control unit, generally, includes a pump, electronic circuitry,conduits for connecting the control unit to the compression device,valves, a source of power, etc., the control unit is usually quitelarge. Hence, the known control units are bulky and heavy. Therefore,positioning of the unit in the device has not been practical becauseattaching the known control units to an outer surface of the compressiondevice would result in an excessive weight burden impairing the mobilityof the user. Integral positioning is also unnecessary as most of theprior art devices are used in a hospital setting where mobility of thepatient is not the main concern. Were the control unit to be positionedon the device, weight would be localized at the attachment point of thedevice resulting in a weight imbalance on the compression device. Also,a bulky control unit protruding from an outer surface of the compressiondevice permits the unit to be knocked and possibly broken when the useris mobile and would not fit beneath clothing.

There are barriers to reducing the size of the control unit. Theconduits between the pump and the inflatable cells have in the past beenexternal and would thus present a trip or tangle hazard. The powerconsumption by the components in a typical hospital device would makethe battery too large to be carried on the device itself and would makeit too bulky to fit under clothing.

The above disadvantages may contribute to low patient compliance andlimit use. A control unit which is an integral part of a device with alow profile and whose internal components are miniaturized sufficientlyso as not to affect the performance of the control unit or the medicaldevice has therefore been sought.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda control unit for a medical device wherein the control unit comprises apump, a conduit and control means for controlling the flow of fluid fromthe pump through the conduit characterized in that the conduit is arigid internal passage located in the control unit.

The control unit of the invention has the advantage that, as theconduits are rigid it is possible to make a detachable connectionbetween the control unit and a docking unit which is part of the medicaldevice. This also makes it possible for there to be no external conduitsbetween the control unit and the docking unit on the medical device. Inthis way, the control unit can be readily attached and detached from themedical device.

According to a second aspect of the present invention, there is provideda control unit assembly for a medical device wherein the assemblycomprises a control unit and a docking unit, the docking unit located onthe medical device wherein

-   -   a. the control unit comprises a pump, a conduit and control        means for controlling the flow of fluid from the pump through        the conduit; and    -   b. the docking unit comprises a detachable fluid transfer        connector which connects the conduit to an inflatable cell of        the device.

Preferably, the docking unit also comprises a backing plate and theconnector is a relatively inflexible connector of the plug and sockettype. The connector, preferably, forms an air tight seal and allows therepeated attachment and removal of the control unit. The number andarrangement of the connectors will be adapted to suit the number ofcells present in the device.

The provision of the backing plate with rigid connectors permits directinsertion of the control unit into the device and allows it to beremoved and re-inserted. This overcomes the need for remote positioningof the control unit assembly. Instead, the pump draws air or fluid froman external source into the conduits and to the rigid fluid transferconnectors of the backing plate into the cells of the compressiondevice.

The rigid connectors, where present, act to hold to the control unitassembly securely while permitting the control unit to be readilydetached from the compression device. To assist in the securement of thecontrol unit to the device, an additional press-fit retaining meanswhich acts against a spring bias and can be released by the pressing ofa button on the control unit may be provided.

The presence of the docking unit and the detachable fluid connectorsgives the advantage that the control unit is removable and, therefore,reusable. This is because typically the control unit assembly issignificantly more costly to produce. Designed as a separate unit, itcan have a working life of many years and can be transferred betweendevices and between patients. For cost-effective treatment of patients,the recycling of the control unit, rather than its disposal after eachpatient, is desirable. In contrast, the medical device whose innersurfaces come into contact with the patient's skin are typically singleuse and disposed of once no longer required by a particular patient. Inany case, compression devices will typically have a working life of nolonger than six months. Hence, the easy removal of the control unitassembly from the medical device and replacement on another medicaldevice is advantageous. The invention further provides that the conduitsin the control unit are preferably rigid internal passages whollylocated within the control unit in the form of a manifold.

The term “manifold” means the fluid transfer conduits that form alabyrinth of passages in the rigid material of the control unit.Preferably, the conduits terminate in connectors suitable for makingconnections with other components of the control unit assembly andcompression device. The manifold replaces the plurality of tubes betweenthe pump and device and makes the control unit compact enough to bereceived in the docking unit. The docking unit is, preferably, a pouchwithin the outer contour of the device.

Preferably, the control unit further comprises a plurality of valveslocated between the pump and the conduits, the plurality of valves beingarranged in a ranked or tiered hierarchical structure

The term “hierarchical or ranked valve tree structure” means the thatvalves are arranged in ranks according to their proximity in thedirection of fluid flow from the pump. The valve closest to the pumpdirects fluid flow to a further rank or ranks of valves. In this manner,the number of valves needed in the control unit to control the pluralityof inflatable cells is reduced.

The provision of the ranked valve arrangement permits size reduction ofthe control unit by reducing the number of valves and, therefore, thespace that they occupy and their power consumption. This permits theproximal positioning of the control unit assembly on or within an outersleeve of a compression device. When placed discretely within an outersleeve of the compression device, there are no external edges of thecontrol unit which can be knocked or damaged during use resulting inimproved patient safety, quality of patient life and control unit life.Furthermore, improved patient compliance is expected with such adiscretely concealed unit.

The ranked valve tree structure of the valve assembly where present,advantageously provides a means of selectively varying the air or fluidpressure of individual cells in the compression device withoutsimultaneously activating all of the valves. Furthermore, the rankedvalve tree structure reduces the number of valves required to achievepressure variation. The tree structure thus permits size reduction inthe control unit as fewer valves are needed. Hence, this arrangement isparticularly amenable to portable power sources such as a battery. Thevalves are preferably latching valves as they further reduce the powerconsumption in the device.

Further, according to the invention, a compression device for use on alimb comprising a control unit assembly according to the first andsecond aspects of the present invention is provided.

Preferably, the one or more detachable fluid transfer connectors of oneaspect of the invention is adapted for connection with the air or fluidtransfer conduits in the control unit and in the compression device.More preferably, this is achieved by a male connector tube on thecontrol unit assembly being engageable with a female connector slot onthe compression device or a female connector slot on the control unitassembly being engageable with a male connector tube on the compressiondevice.

A latch can be used to retain the male and female parts in place inorder to secure the control unit. Preferably, the latch can be easilyreleased so that the control unit assembly can be removed from thecompression device, for example, by pushing a button on the exterior ofthe compression device.

Any number of rigid air or fluid transfer connectors can be employed.However, preferably, four or five connectors will be present and thiswill be dependent on the requirements of the compression device.Preferably, the air or fluid transfer connectors are made of a rigidplastics material which can be integrally formed as part of the backingplate. This may be achieved, for example, by means of injection moldingtechniques during the manufacture of the docking unit or backing plate.

The control unit assembly of the first and second aspects of theinvention may comprise an additional (booster) portable battery as apower source. This may be a re-chargeable nickel cadmium, nickel metalhydride or lithium ion battery or any other lightweight battery thatprovides sufficient power.

Preferably, the control unit is attached to the backing plate in asliding press-fit to engage the connectors and the latch.

The compression device, preferably, has an outer surface with a pouchfor receiving and holding the control unit assembly. The docking unit ispositioned in the pouch and can conveniently be in the form of a backingplate.

The compression device may contain many inflatable cells dependent onthe individual needs of a patient and may be adapted for an arm or aleg.

In a preferred embodiment, the device is adapted for use below the kneeof a patient and comprises three inflatable cells located in the regionbetween the knee and the ankle and two inflatable cells located in theheel and foot region.

In another embodiment, the invention provides a control unit assemblyfor a medical device wherein the assembly comprises a control unit and adocking unit, the docking unit located on the medical device wherein thecontrol unit comprises a pump, a conduit and control means forcontrolling the flow of air through the conduit and the docking unitcomprises a detachable air inlet connector which provides air to thepump, the connector being provided with a filter.

In this way, the air inlet to the pump is provided with a filter on thedevice side of the assembly. Thus, when the device has reached the endof its useful life and is replaced, the control unit is indirectlyprovided with a new filter. If the filter were placed in the controlunit, it would not be replaced during the lifetime of the control unitwithout servicing of the unit. In addition, the provision of the filteron the device side of the assembly means that contamination of thecontrol unit and its electrical circuitry is limited. If the filter werepresent in the control unit, during operation of the device unfilteredair would be drawn into the control unit at least as far as the filter.As the filter is external to the control unit, only filtered air isdrawn into the control unit. This gives the advantage that reliabilityof the control unit may be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the control unit assembly of theinvention integrated in a mobile compression device worn on the limb ofa patient.

FIG. 2 is a perspective view of a backing plate for receiving a controlunit to form the assembly of the invention.

FIG. 3 is a perspective view of one end of the control unit of theinvention showing the connectors which engage the connectors of thebacking plate in use.

FIG. 4 is a perspective view of the backing plate and control unit ofthe assembly removed from the compression device to show the comingtogether of the connectors and the springs which bias the assembly apartfor detachment of the control unit.

FIG. 5 is a schematic air flow logic diagram of the assembly of theinvention.

FIG. 6 is a schematic view of the interior of the control unit of theassembly of FIG. 1 showing the air manifold.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 a control unit assembly and compression device according to anembodiment of the invention is shown worn on the leg of a patient. Thedevice comprises a sleeve 2 having a leg cuff 4 connected to a foot cuff6. The device also comprises a control unit assembly 8 comprising acontrol unit 10. The control unit 10 is small and when removed from thesleeve 2 may be hand held. The control unit 10 is battery powered andrechargeable so that it can be recharged when attached to or detachedfrom the sleeve 2. FIG. 1 also shows the pouch 12 provided on sleeve 2for receiving the control unit 10 and the low profile of the assembly.The control unit assembly follows the contour of the device andintegrates the assembly into the device.

FIG. 2 is a perspective view taken from above the device with thecontrol unit 10 removed showing the interior of the pouch 12 and thebacking plate 14. The control unit 10 may be slidably engaged in thepouch 12 and retained in position by a latching means. FIG. 1 shows arelease button 22 positioned on the pouch 12 of the device which whendepressed releases the control unit 10 from the pouch 12.

FIG. 3 is a perspective view of the control unit 10 removed from thepouch 12 and viewed from the bottom, showing the connectors 16 forengagement with the rigid connectors 18 of the backing plate 14.

FIG. 4 is a perspective view of the backing plate 14, removed from thedevice for the purposes of illustration, showing the rigid connectors 18for engagement with the connectors 16 of the control unit 10. FIG. 4shows the control unit 10 being slid into engagement with the backingplate 14. As the control unit 10 is slid into the backing plate 14, itbegins to compress two springs 20 which act to bias the control unit 10and backing plate 14 apart. Further sliding movement of the control unit10 causes the connectors 16, 18 to engage in a fluid tight seal and thecontrol unit 10 to engage a latch (not shown) which retains the controlunit 10 in the pouch 12 against the springs 20. The control unit 10 isreleased from the pouch 12 by depressing button 22 (FIG. 1), the outlineof which is visible on the sleeve 2. The springs 20 then cause thecontrol unit 10 and backing plate 14 to spring apart and the controlunit 10 can be removed from the device. The springs 20 can be in theform of a leaf spring located in the backing plate 14 which similarlybiases the parts of the assembly apart.

FIG. 4 also shows air filter 24 provided on the air inlet/outletconnector of the backing plate 14. As the air filter 24 is provided onthe backing plate 14, it is naturally replaced when the control unit 10is used with a new device. This reduces the service requirements of thecontrol unit 10.

Referring to FIGS. 5 and 6, the control unit 10 has fluid flow conduits40, 42, 44, 46, 48 which terminate in connectors C1, C2, C3, C4 and anair inlet/outlet C5. When a cell is required to be inflated, air istaken in via the conduit 48 by the operation of pump (labeled “PUMP”)and valves V4 and V5 under instruction from a processor (not shown). Theprocessor instructs valves V3, V1 and V2 which are arranged between theair inlet/outlet C5 and the conduits 40, 42, 44, 46 such that only oneof the conduits 40, 42, 44, 46 is operational at any one time. From FIG.5 it can be seen that valve V3 directs fluid from/to the airinlet/outlet C5 to/from either valve V1 or V2 which in turn selectivelyopen or close fluid paths to connectors C1 or C2, or C3 or C4. Thevalves are preferably latching valves.

A sensor S1 (FIG. 6) is located in conduit 40 between connector C1 andvalve V1 in the control unit 10. Similarly, sensors S2, S3 and S4 arelocated in conduits 42, 44, 46, respectively. Sensors S1 to S4 are allfluid pressure sensors controlled by a processor (not shown) andarranged to provide an indication of pressure exerted by the respectivecells in the device. S5 independently monitors the pressure in the fluidflow system of the device.

FIG. 6 also shows the air manifold 50 with its labyrinth of passagesthat supplies air from the pump to each of the connectors C1 to C5. Theair manifold 50 replaces the external tubes needed with prior artdevices between a distal control unit and the connectors of the device.

1. A control unit for a medical device comprising a pump, a conduit andcontrol means for controlling the flow of fluid from the pump throughthe conduit wherein the conduit is a rigid internal passage located inthe control unit. 2.-22. (canceled)